The number of echoes combined into a single image or image set in multiple echo imaging sequences or echo-train techniques such as rapid acquisition with relaxation enhancement (RARE), fast-spin echo (FSE), and turbo spin-echo (TSE). In RARE imaging, the ETL typically equals the acceleration factor.
As for tooth pain, it is caused by a reaction of the nerves inside a tooth's pulp chamber with the severity dependent upon the type and degree of the stimulus. What follows are some examples of symptoms you may be feeling and their possible causes.
Toothache & Tooth Pain Guide! What is a Toothache? Toothache is pain typically around a tooth, teeth or jaws. In most instances, toothaches are caused by a dental problem, such as a dental cavity, a cracked or fractured tooth, an exposed tooth root, or gum disease. Sometimes diseases of the jaw joint (temporomandibular joint), or spasms of the muscles used for chewing can cause toothache like symptoms.